1. Field of the Invention
The present invention relates to an image forming apparatus and control method therefor.
2. Description of the Related Art
There is proposed an apparatus which forms an image by an electrophotographic process of irradiating a photosensitive drum serving as an image carrier with a laser beam or light from a light-emitting element (e.g., LED: Light Emitting Diode) that is modulated in accordance with recording information.
For example, there is proposed a color image forming apparatus having a plurality of image forming units which develop electrostatic latent images formed on photosensitive drums and transfer toner images of respective colors onto a transfer sheet or intermediate transfer belt.
A monochrome image forming apparatus is also proposed which develops an electrostatic latent image formed on one photosensitive drum and transfers a black toner image onto a transfer sheet.
For these image forming apparatuses, there is proposed an arrangement example of a copying machine which connects to a document scanning apparatus and sends document image information to an image forming apparatus to copy the document image.
For example, Japanese Patent Laid-Open No. 11-292335 and Japanese Utility Model Laid-Open No. 2-29063 each disclose an example of a combination of a paper feed unit and image forming apparatus. These references propose image forming apparatuses in each of which a plurality of paper feed units serving as the base of the image forming apparatus stack up replaceably and the bottom of the main body of the image forming apparatus has an opening for receiving sheets conveyed from the paper feed units.
An image forming apparatus is also proposed which can connect to a post-processing apparatus called a finisher for sorting transfer sheets printed by the image forming apparatus into respective copies or stapling respective copies. An image forming apparatus of this type and various post-processing apparatuses connectable to the image forming apparatus can operate to perform a series of printing and post-processing operations in cooperation with each other.
Some document scanning apparatuses have various scanning resolutions such as 400 dpi (dots per inch) and 600 dpi. A full-color image forming apparatus generally has a full-color CCD sensor which converts a scanned document image into a full-color image signal. A monochrome image forming apparatus often has a monochrome scanning CCD which converts a scanned document image into a monochrome image signal. Even for a monochrome image forming apparatus, a document scanning apparatus is proposed which has a full-color CCD sensor and converts a document image into a full-color image signal. Recently, a product is proposed which provides a scanner function of transmitting image information scanned by a document scanning apparatus to a desired destination via a network.
As described above, an apparatus arrangement is proposed in which an image forming apparatus cooperates with another apparatus to provide a function unimplementable by the single image forming apparatus.
Various proposals are also made for an apparatus arrangement which permits exchanging part of an image forming apparatus. For example, there is proposed an apparatus form which permits newly assembling a double-sided paper conveyance unit into an image forming apparatus of standard specifications. An image forming apparatus is also proposed in which some units in the apparatus are made detachable so that the functions of the image forming apparatus can change into an apparatus arrangement conforming to product specifications desired by a user.
There is also proposed an image forming apparatus of an arrangement which permits connecting the image forming apparatus to a controller arranged outside the image forming apparatus or assembling a controller into the image forming apparatus.
Conventionally, the user selects, from various image forming apparatuses, an image forming apparatus which implements desired functions, performance, user friendliness, and the like. To obtain a function, performance, or the like which cannot be attained by the selected image forming apparatus, the user selects an apparatus arrangement so as to utilize the desired function, performance, or the like by combining the image forming apparatus with various exchangeable apparatuses, various units, various controllers, and the like.
A conventional image forming apparatus can perform various operations by executing a system operation in cooperation with various apparatuses, various units, various controllers, a host computer, and the like, and provides a user with various conveniences.
In general, a post-processing apparatus such as a finisher is controlled to determine its operation in accordance with the printout operation mode of an image forming apparatus. There is no image forming apparatus which controls the operations of at least two subsystems to execute a series of image output operations and a series of information processing operations for image information almost simultaneously or independently.
A conventional image forming apparatus poses various problems owing to the above arrangement.
Since the conventional image forming apparatus executes a system operation in cooperation with various apparatuses, various units, various controllers, a host computer, and the like, it only operates depending on its operation mode, function, and performance.
For example, when the image forming apparatus connects to a paper feed apparatus or finisher, the apparatus combination may limit their functions and performance associated with apparatus control under restrictions on functions and performance.
For example, the image forming apparatus and finisher exchange communication information, and the finisher determines its operation mode, performance, and functions and operates in accordance with the operation of the image forming apparatus. The arrangement of the image forming unit, paper feed unit, and paper conveyance unit in the image forming apparatus also determines the whole operation performance of the image forming apparatus.
Among various apparatus arrangements, there is no apparatus arrangement which can flexibly meet the user's need in terms of the operation of the entire system such as a print operation or a cooperative operation (e.g., a print operation or scan operation) with a host computer.
That is, when weighting operation specifications in order to cope with customization to apparatus operation specifications desired by a user, apparatus specifications implementable by exchanging a subunit cannot be fully enhanced unless operation specifications can be determined on the basis of association with control information.
It is necessary and important to maintain the image formation quality with a combination of subsystems different in performance in an image forming apparatus made up of a plurality of subsystems.